In many lighting situations, it is necessary to have constant illumination of a certain quality. For example, in automotive lighting, it is necessary for headlights, taillights, and warning lights to be visible and at a certain luminance at all times. This can be for safety reasons or to reduce financial penalties for insufficient lighting. For example, in the trucking industry a truck can be financially penalized if it does not have the regulated amount of lighting functioning properly.
Lighting elements only last a fixed time, however, and will eventually burn out, in part or in whole, due to age, damage, or defect, providing diminished light output, and requiring replacement. This leads to the double problem of noticing that the some or all of the lights in a light source have burned out, and having the materials and facilities to properly replace the burned out lights. In practice, it often takes some time to notice that lights are burned out, and once they are noticed, it takes even more time to get them replaced.
It would therefore be desirable to provide a lighting device that will automatically provide the desired level of lighting even if components within the lighting device cease to function. One way to achieve this is to automatically switch to an alternate, more luminescent lighting set when all or part of a current lighting set burns out.
It would also be desirable to provide a lighting device that warns a user when a light burns out in the device.